Melanoma patients with higher levels of a protein called S-100 in their blood may run a higher risk of having the potentially deadly skin cancer return, a new study says.

The study tested serum samples from 103 patients who were treated with high-dose interferon, a standard therapy for melanoma; the patients had been treated eight years earlier, on average. The disease recurred in 64 of the patients within an average of 30 months. When the researchers examined levels of S-100 in the serum samples, they found that the higher the level of the protein, the greater likelihood the patient's disease had returned.

"Melanoma patients who initially respond well to treatment with interferon are at high risk of their cancer recurring," said Dr. John Kirkwood, principal investigator of the study and a professor of medicine at the University of Pittsburgh School of Medicine and director of the school's Melanoma Center. "We know that only 30 percent of these patients benefit from treatment long-term. The goal of our study was to identify better predictors of who will benefit most from treatment with interferon and who is most at risk of their cancer returning."

The study also found that patients who survived longer showed increased evidence of an autoimmune response to treatment with interferon.

The study findings were to be presented Saturday at the annual meeting of the American Society of Clinical Oncology, in Chicago.

"With further study, we hope to learn more about the role of S-100 in melanoma survival," said Joseph Stuckert, a medical student at the University of Pittsburgh School of Medicine who was to present the study at the meeting. "S-100 may be an important key to better stratifying patients into those more or less likely to relapse."

The next step in the research, Stuckert said, is to identify factors that may make patients more likely to develop autoimmunity and to further examine the role of S-100 as a potential biomarker for melanoma.

Malignant melanoma is one of the deadliest forms of skin cancer. Nearly 60,000 new cases of melanoma are expected in 2007, and 8,100 deaths are expected to occur.

The study was funded by a grant from the U.S. National Cancer Institute.